Process for the manufacture of decolorizing carbons



Patented May 12, llhzf'n $CAR Ii. BARNEBEY, 01* DETROIT,

FPROCESS FUR THE MAN UFAC'ILURE (ll? DECQLQREZING- No Brewing.

To all whom it may concern:

Be it known that l, OSCAR L. BARNEBEY, a citizen of the United States, residing in Detroit, county of Wayne, and State of Michi- 5 gan, have invented certain new and useful Improvements in a Process for the Manufacture of Decolorizing Carbons, of which the following is a specification.

The invention relates to a process of treating vegetable materials, especially plants now regarded as waste materials of practicall no value, with the object of securing" valua le products including good gas adsorbent and decolorizing carbon, silica, potassium salts, phosphates and such other ingredients as the particular plants contain. lln my co-pending applications, Serial Nos. 455:,972 and 454,973, it set forth the recovery of such products by methods different from the one constituting this invention. I This invention is particularly applicable to plants, and still more particularly to the stalks and straw and leaves of plants, such as oats, rice, corn and similar field crops, which possess a relatively high silica content,

although it can be applied with success to plants of lower content of silica as well.-

In its preferred form, my process includes, first, charring the vegetable matter to remove all or practically all of the hydrocarbons. Then the carbonized material is treated with concentrated fluo-silicic acid (H SiF usually in the presence of a strong mineral acid suchv as hydrochloric acid or sulfuric acid. The mass is then heated, volatilizing the silicon as silicon tetrafluoride, thus removing the same from the carboni During this heating period, the basic constituents such as magnesia, iron oxide, lime, potash,-etc., along with phosphates, chlorides, sulfates and similar salts are dissolved in the mineral acid solution. The carbon is then filtered and the soluble salts Washed out, after which the carbon is dried. Reheating the dried carbon. may be performed in special cases to improve the roduct, although usually this improvement is not great enough to warrant the second furnace o eration. Such reheating may be accomplis ed at temperatures similar to those used: in carbonization, or slightlyv higher if necessar since at this stage of the pgpcess the solub' e and fusible salts have n removed.

The carbonization of the vegetable ma- .llpplieation filed March 23, 1921. fierial It'o. 254,971.

terials is accomplished in such a manner as to avoid fusing the ash constituents into the carbon. Also the temperature is maintained as low as possibleto prevent shrinkage of the carbon nucleus itself. The carbonization is conducted in such a manner as to leave substantially no hydrocarbons in the carbon. While the temperature used can be of av relatively wide range, depending essentially upon the length of time the material is heated and upon the method of removal of the products of distillation, it has been found that the temperature range from 400 C. to 700 C. is most satisfactory. llhe best general practice is to remove the distillation products as rapidly as they are produced. Such products can be burned to furnish heat for retorting and for any other useful purpose, or they can be separated and purified to yield tar, acetic acid or acetate, alcohol and acetone; However, such purification and separation is not inherently a part of this invention, hence is not described.-

The volatile silicon tetrafiuoride, pro

duced by action ofthe fiuo-silicic, acid with the silica or. silicates, is passed into an excess of water with which it reacts to produce silicic acid and regenerates fiuo-silicic acid as follows:

3Sill 1+3H O+XH o:

eii sir n sio nnp.

acid solution obtained from the filtered hydrated silicic acid-is suitably concentrated by evaporation and when thls concentrated solution is added to the next batch of carbonized material, the acid reacts with the silica thus:

SiO +2H SiF =3SiF +2H O or with silicates, illustrated by calcium silicate (CaSiO thus:

'In other words, the fluo-silicic acid has a.

capacity to react with the silica as such or in silicate combination in the ratio of 2-1 molecularly.

Since the silicon tetrafluoride on decom-. position precipitates only one-third of its silicon and converts the remaining twothirds to fluo-silicic acid, it is thus seen that two-thirds of the silicon involved in each cycle of treatment is carried as bound fluorine in order to maintain' the proper amount of, active hydrofluo-silicic acid available for reaction, The amount of silica removedfrom any particular carbonized ma-. terial can be regulated to leave any desired amount of silica in the carbon and likewise the percentage of mineral acid which is added to each batch can be so regulated to leave any desired percentage of basic constituents in the particular carbon.

The .following examples will serve to further explain my invention:

Example 1. Rice hulls from a rice mill are carbonized at a temperature of redness (500 to 600 C.) without access of air until carbonization is complete; as shown by cessation of evolution of any appreciable quantities of tar, pyroligneous acid and other gases. The carbonized material consists of approximately 55% mineral matter and 45% carbon, and of this percentage of mineral matter, 85% is silica.

The carbonized material containing the silica is treated with three times its weight of 40% solution of fiuosilicic acid. Hydrochloric acid, to the amount of 10% by a weight of the carbonized material, is also acid. An excess of water is used to assist the separation of the silicic acid.

- rice material.

added.

The solution is heated to boiling, and the silicon-tetrafiuoride thereby evolved is passed into water which converts the same into silicic acid and regenerated fluosilicic in When the reaction is completed, as shown by the fact that no more silicon tetrafluoride is evolved, an excess of water is added to the carbonized'material and the carbon filtered and washed. The washed carbon is heated to redness to thoroughly dry the carbon and also to remove the slight traces of hydrochloric acid which remain. The silicic acid, on the other hand, is filtered out, washed and dried. r

i The solution of fluosilicic acid which has been regenerated is concentrated somewhat by boiling in order togive ap roximately'a 40% solution, in which state t is ready to be used again with the next lot of carbonized By the use of this process the fluosilicic acid can be used over and over again with only sufficient additions thereto to make up for the fluosilicic acid mechanically lost in carrying out the process.

The product secured is a ve excellent decolorizing carbon, and in a dition the silicic acid recovered is of commerci a1 value.

Example 2. Bagasse from a cane mill is carbonized at redness (500 to 600 C.) without access of air, after which the carbon is heated to a temperature of 7 900 C. in the presence of oxygenated gases which are likewise of that temperature.

By oxygenated gases I mean gases of the nature of steam (H O), carbon dioxide S and combustion gases (essentially H 0 and N The second stage of ,carbonizing is continued until to by weight of carbonized material is eliminated by reaction. The resulting carbonized material is treated with twice its weight of 40% fluosilicic acid solution and one-tenth of its weight of sulphuric acid according to the procedure described in Example 1 regulating the amount of air admitted to the carbonizing zone during the second stage, the 30% to 60% by weight of'carbonized material can be removed and the use of ox genated gases, other than those forme by reaction, can be obviated. Also the two steps can, if desired, be combined into one by gradually heating the material to 700-900 in the presence of a regulated ainount of air, such regulation being accomplished to remove 30 to 60 per cent of the carbonizing material, the reaction being controlled to furnish the heat needed for carbonizing.

Since the various vegetable carbonized materials from different sources are widely different in the relation of basic and silica content, the ratio of the quantity of fluosilicic acid and mineral acid used willvary with the different sources of plant materials.

The only loss of fiuo-silicic acid in this process is due to mechanical losses of operation, and in consequence of this fact only suflicient fiuo-silicic acid need be added to the operating process to supply such mechamcal losses as occur from time to time.

This process is a very economical one is easy of control and produces carbon of high decolorizing value. The process can be varied quite widely within the sco e of the appended claims to meet the speci c conditions involved for any particular material, in fact either vegetable or mineral carbonaceous material can be processed as above outlined.

What I claim as my invention is:

1. A process of manufacturing decolorizing carbons. comprising charring carbonaceous sllicon-contamlng material, and removmg the sllica by reaction I with fluosilicic acld.

2. A process of manufacturing decolorizing carbons comprising charring carbonaceous silicon-containing material, and removing the silica by reaction with fluosilicic acid and a mineral acid.

3. A process of manufacturing decolorizing carbons comprising charring carbonace-" ous silicon-containing material, and removing the ash constituents by reaction with fluosilicic acid and hydrochloric acid.

4. A process of manufacturing decolorizing carbons comprising charring carbonaceo'us silicon-containin material at temperatures from 400 to 00 Ci, and removing silicic acid and hydrochloric acid solutions.

7 Aprocess of manufacturing decoloriz-' ing carbons comprising charring carbonaceous silicon-containin material at temperatures from 400 to 00 0., removing ash constituents by heating with fluosilicic acid and a mineral acid solution, filtering and washing the carbon, drying the carbon, and again heating the resultant carbon to a temperature of 400 to 700 C.

8. A process of manufacturing decolorizing carbons comprising charring carbonaceous silicon-containing material, removing the silicon with fluosilicic acid, andremoving base constituents as soluble salts of mineral acids.

9. A continuous extraction process of removing silica from carbomzed sllicon-containing material comprising treating the latter with fluosilicic acid, volatilizing the resulting silicon-tetrafluoride, decomposing said silicon tetrafluoride with water to regroduce fluosilicic acid, and recovering the uosilicic acid for'subsequent use.

-10. A continuous extraction process of removing silica from carbonized silicon-containing material comprising treating the latter with fluosilicic acid, volatilizing the resulting silicon tetrafluoride, causing interaction of silicon tetrafiuoride with water to regenerate fluosilicic acid, and making cyclic utilization of said fluosilicic acid for the treatment of additional carbonized material.

In testimony whereof, I hereunto afiix my signature.

. OSCAR L. BARNEBEY. 

